Answer:
18.018 seconds.
Explanation:
Given that the half life of Manganese, Mn = 3 seconds. The initial sample mass = 90.0 gram, the final sample mass = 1.40 gram.
The general idea to the question is to look for the time it will take to decay from the initial mass that is 90 gram to 1.40 gram.
Therefore, we will be making use of the formula below;
J(t) = J(o) × (1/2)^t/t(hL).
Where t(hL) is the half life, t is the time taken, J(t)= mass after time,t and J(o) is the initial mass. So, let us slot in the values into the equation above.
1.4 = 90 × (1/2)^ t/3.
1.4/90 = (1/2)^t/3.
t/3 = log(0.5) (1.4/90).
+Please note that the 0.5 of the log is at the subscript).
That is the base 0.5 logarithm of (1.4/90) 0.01556 is 6.0060141295.
t = 3 × 6.0060141295.
t = 18.018 seconds.
In my opinion the answer is D
Answer:

Explanation:
Hello!
In this case, given this is an acid-base neutralization and we are considering a diprotic acid, we can write the following mole-mole relationship:

It means that the moles of acid can be computed given the volume and concentration of NaOH:

It means that the approximate molar mass of the acid is:

Best regards!
Open system ( exchanges energy and matter with the surroundings)
Closed system ( exchanges only energy with the surroundings)
Isolated system ( does not exchange energy or matter)
Adiabatic system ( does not allow any heat to be transferred into or out of the system)